JP2013055466A - Dynamic microphone unit and dynamic microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic microphone unit and a dynamic microphone capable of reducing impact sound to be generated when a diaphragm is largely displaced.SOLUTION: A dynamic microphone unit includes: a diaphragm 5 to be oscillated by receiving a sonic wave; a voice coil 6 fixed to the diaphragm 5 and to be oscillated together with the diaphragm 5; a magnetic circuit including a magnetic gap with the voice coil 6 arranged therein and generating a magnetic field in the magnetic gap; a rear air chamber 15 that is formed on the rear surface side of the diaphragm 5; and a second air chamber 9 formed in the posterior part of the voice coil 6 and communicating with the rear air chamber 15. In the second air chamber 9, a thin plate-like acoustic resistor 50 with elasticity is arranged with tension at a position for limiting the capacity of the second air chamber 9 and also allowing the voice coil 6 to have contact within the maximum displacement.

Description

  The present invention relates to a dynamic microphone unit and a dynamic microphone. In particular, the present invention aims to reduce an impact sound generated when a diaphragm is greatly displaced due to excessive sound pressure.

  The omnidirectional component of the dynamic microphone is resistance control. Therefore, the frequency response can be flattened by arranging the acoustic resistance immediately after the diaphragm.

  7 and 8 show an example of a conventional dynamic microphone unit. 7 and 8, reference numeral 1 denotes a unit case that forms the base of the microphone unit. The unit case 1 has a cylindrical shape with a bottomed outer shape, and an inner cylinder 11 extending downward from the upper end portion is formed in the inside by integral molding, and a lower end portion of the inner cylinder 11 extends radially inward. A round collar 12 is formed.

  A magnetic circuit is configured by housing the following magnetic circuit forming member in the inner cylinder 11 of the unit case 1. First, a petri dish-like yoke 2 is fitted in the inner cylinder 11 and supported by the flange 12 of the inner cylinder 11, and the outer peripheral surface of the peripheral wall of the yoke 2 is in contact with the inner peripheral surface of the inner cylinder 11. Yes. A disk-shaped magnet 3 having an outer diameter smaller than the inner diameter of the peripheral wall of the yoke 2 is fixed on the bottom plate of the yoke 2, and a disk-shaped pole piece 4 is fixed on the magnet 3. A ring yoke 21 is fixed to the upper end surface of the peripheral wall of the yoke 2. The pole piece 4 and the ring yoke 21 have substantially the same thickness and are fixed at substantially the same height. The outer peripheral surface of the pole piece 4 and the inner peripheral surface of the ring yoke 21 are opposed to each other at an appropriate interval. A magnetic gap is formed. The magnetic circuit constituent member is accommodated in the inner cylinder 11 so that the upper end surface of the pole piece 4 and the upper end surface of the inner cylinder 11 are at substantially the same height.

  The magnetic flux emitted from the magnet 3 returns to the magnet 3 through a magnetic circuit composed of the yoke 2, the ring yoke 21, the magnetic gap, and the pole piece 4. Therefore, the magnetic flux crosses the magnetic gap. The outer diameter of the magnet 3 is smaller than the outer diameter of the pole piece 4, and an air chamber 9 is formed below the magnetic gap between the outer peripheral surface of the magnet 3 and the inner peripheral surface of the inner cylinder 11. The outer diameter of the magnet 3 is smaller than the outer diameter of the pole piece 4, and an air chamber 9 wider than the magnetic gap is formed on the outer peripheral side of the magnet 3 below the magnetic gap. A plurality of holes 22 are formed in the yoke 2 so as to vertically penetrate a portion corresponding to the bottom thereof, and the holes 22 connect the space surrounded by the air chamber 9 and the circular flange 12 of the unit case 1. It is out.

  A protruding edge 14 is formed at the upper end of the unit case 1 along the outer periphery of the unit case 1, and the upper end of the unit case 1 is inward of the protruding edge 14 and more than the protruding edge 14. A protrusion 13 is formed at a lower position along a circle concentric with the protrusion 14. The outer peripheral edge of the diaphragm 5 is fixed to the upper surface of the protrusion 13. The diaphragm 5 is made of a synthetic resin or metal thin film, and includes a center dome 51 and a sub dome 52 surrounding the center dome 51 by molding the material. The center dome 51 has a shape obtained by cutting a part of the spherical surface, whereas the sub dome 52 has a partial arc shape in cross section and is formed continuously to the outer peripheral edge of the center dome 51, and the outer peripheral edge of the sub dome 52 is the protrusion 13. It is fixed to the upper surface of the. Since the outer peripheral edge of the sub dome 52 is fixed as described above, the diaphragm 5 vibrates in the front-rear direction (vertical direction in FIG. 7) using the outer peripheral edge of the sub dome 52 as a fulcrum when receiving sound waves. can do.

  The voice coil 6 is fixed to the diaphragm 5 along a circular boundary line between the center dome 51 and the sub dome 52. The voice coil 6 is formed and solidified by winding a thin conducting wire, and one end of the cylindrical shape is fixed to the diaphragm 5. With the outer peripheral edge of the sub dome 52 of the diaphragm 5 fixed as described above, the voice coil 6 is positioned within the magnetic gap, and the voice coil 6 is separated from the ring yoke 21 and the pole piece 4. ing.

  On the front side of the diaphragm 5, an equalizer 8 that also serves as a protective member for the diaphragm 5 is disposed by fixing its outer peripheral edge to the protruding edge 14 of the unit case 1. The ceiling surface of the central portion of the equalizer 8 is formed in a dome shape, and a gap with a constant interval is maintained between the diaphragm 5 and the center dome 51. The equalizer 8 has a plurality of holes 82 for guiding sound waves from the outside to the diaphragm 5.

  The lower end of the unit case 1 is closed, and a relatively large air chamber 15 is formed inside the unit case 1. An acoustic resistor 16 is disposed in close contact with the lower surface of the yoke 2. The inner peripheral surface of the flange portion 12 of the unit case 1 is a cylindrical surface, and the outer periphery of the acoustic resistor 16 is supported by the inner peripheral surface of the flange portion 12. The acoustic resistor 12 is formed by stacking thick nonwoven fabrics or the like. The acoustic resistor 16 is disposed on the back side of the diaphragm 5, and the space on the back side of the diaphragm 5 communicates with the acoustic resistor 16 through the magnetic gap, the air chamber 9, and the hole 22 of the yoke 2, and further the air chamber. 15 leads to.

  When the diaphragm 5 receives a sound wave, it vibrates back and forth according to the change in the sound pressure, and the voice coil 6 vibrates forward and backward together with the diaphragm 5. When the voice coil 6 vibrates, the voice coil 6 crosses the magnetic flux passing through the magnetic gap, and the voice coil 6 generates an audio signal corresponding to the change in sound pressure. In this way, electroacoustic conversion is performed, and for example, audio signals are output from both ends of the voice coil 6 routed along the back surface of the subdome 52.

  According to the dynamic microphone unit configured as described above, the space on the back side of the diaphragm 5 is divided into the space on the back side of the center dome 51 and the space on the back side of the sub dome 52 by the voice coil 6. The voice coil 6 communicates with the inner peripheral surface side magnetic gap and the outer peripheral side magnetic gap. In order to increase the sensitivity of the dynamic microphone unit, it is effective to narrow the magnetic gap. Therefore, the magnetic gap is narrowed as much as possible without the voice coil 6 contacting the pole piece 4 and the ring yoke 21. Yes. Therefore, the space on the back side of the diaphragm 5 is substantially the same as that divided by the voice coil 6 into the back side space of the center dome 51 and the back side space of the sub dome 52 as described above.

  Now, the acoustic capacity of the back side space of the center dome 51 is Sc, the acoustic capacity of the back side space of the sub dome 52 is Ss, and the gap formed between the inner peripheral surface of the voice coil 6 and the outer peripheral surface of the pole piece 4 is The acoustic mass is mgi, the acoustic resistance is rgi, the acoustic mass due to the gap formed between the outer peripheral surface of the voice coil 6 and the inner peripheral surface of the ring yoke 21 is mgo, and the acoustic resistance is rgo. The sound pressure applied to the diaphragm 5 from the front side is P1, the acoustic resistance of the acoustic resistor 16 disposed in the air chamber 11 of the unit case 1 is r1, and the acoustic mass of the front air chamber of the diaphragm 5 is Let mo be the acoustic capacity. Further, when the acoustic capacity of the air chamber 9 generated between the inner peripheral surface of the peripheral wall of the yoke 2 and the outer peripheral surface of the magnet 3 is Sg, the acoustic capacities Sc and Ss of the two spaces are shown in FIG. As described above, the acoustic mass mgi, the acoustic resistance rgi, the acoustic capacitance Sg, the acoustic mass mgo, and the acoustic resistance rgo are connected.

  FIG. 9 is an equivalent circuit of the microphone unit shown in FIGS. 7 and 8 having the above-described acoustic mass, acoustic capacity, and acoustic resistance. As shown in FIG. 9, the sound pressure P1, the acoustic mass mo, the acoustic capacitance So, the acoustic mass mgi, the acoustic resistance rgi, the acoustic resistance rgo, the acoustic mass mgo, and the acoustic capacitance Ss are connected in series. The connection point between the acoustic capacitance So and the acoustic mass mgi, the connection point between the sound pressure P1 and the acoustic capacitance Ss are connected by the acoustic capacitance Sc, the connection point between the acoustic resistance rgi and the acoustic resistance rgo, and the sound pressure P1 The connection point of the acoustic capacitor Ss is connected by the acoustic resistor r1 and the acoustic capacitor S1 connected in series. Further, the acoustic capacitance Sg is connected in parallel to the series connection of the acoustic resistance r1 and the acoustic capacitance S1.

  As apparent from FIG. 9, the inner circumferential acoustic mass mgi of the magnetic gap divided by the voice coil 6 and the acoustic capacitance Sg of the air chamber 9 constitute a resonance circuit, and the outer circumferential acoustic mass of the magnetic gap. Mgo and the acoustic capacitance Ss in the back side space of the sub dome 52 constitute a resonance circuit. The volume of the air chamber 9 is smaller than the volume of the air chamber 11 that occupies the lower half of the unit case 1, and the acoustic capacity Sg tends to resonate in cooperation with the acoustic mass mgi. Yes. When this resonance occurs, a peak occurs at a specific frequency, and the frequency characteristics deteriorate.

  In order to reduce the resonance, it is conceivable that the volume of the air chamber 9 is further reduced so that the acoustic capacity Sg is minimized so that it does not resonate with the acoustic mass mgi. The conventional example shown in FIG. 10 is an example. In this example, the acoustic resistor 25 is disposed in the air chamber 9 generated between the inner peripheral surface of the peripheral wall of the yoke 2 and the outer peripheral surface of the magnet 3, and the acoustic resistor 25 is in contact with the bottom surface of the yoke 2. The air chamber 9 is formed on the upper surface side of the acoustic resistor 25. Therefore, the volume of the air chamber 9 is limited by the acoustic resistor 25, and the acoustic capacity Sg of the air chamber 9 is extremely small. If the acoustic resistance of the acoustic resistor 25 is r1, the acoustic capacitance Sg is connected to the acoustic capacitance S1 through the acoustic resistance r1 and the hole 22 of the yoke 2. This is represented by an equivalent circuit in FIG. In the equivalent circuit shown in FIG. 11, as described with reference to FIG. 10, the acoustic capacitance Sg is limited to an extremely small capacitance that can be ignored due to the presence of the acoustic resistor 25, and thus the illustration of the acoustic capacitance Sg is omitted. Has been. Thus, in the example shown in FIG. 10, resonance caused by the air chamber 9 is less likely to occur, and good frequency characteristics having no peak in the audible frequency band can be obtained.

  As described above, in order to arrange the acoustic resistor 25 in the air chamber 9 behind the voice coil 6 and make the volume of the air chamber 9 extremely small, it is necessary to bring the acoustic resistor 25 close to the voice coil 6. When the acoustic resistor 25 has a felt-like shape, a non-woven fabric, or a structure similar to a non-woven fabric, a part of the fibers constituting the acoustic resistor 25 rises as indicated by reference numeral 251 in FIG. When the vibration plate 5 vibrates greatly, the voice coil 6 comes into contact with the rising edge 25 of the fiber to generate an abnormal noise, and the vibration of the voice coil 6 that is faithful to the sound wave is inhibited, so that the faithful electroacoustic conversion cannot be performed. . Therefore, there is a limit in bringing the acoustic resistor 25 close to the voice coil 6, and there is a limit in reducing the acoustic capacity Sg by limiting the volume of the air chamber 9. There are limits to prevention.

  By the way, there is a dynamic microphone that is used by being attached to a musical instrument in order to collect the sound of the musical instrument. In particular, in a dynamic microphone that picks up the sound of a musical instrument that generates a sound wave with a large sound pressure at a low frequency, such as a bass drum, the diaphragm is greatly displaced, so the voice coil lead-out part is the yoke corner and diaphragm. It may be disconnected between the two. Therefore, the present inventor has found that the maximum displacement position when the diaphragm swings toward the pole piece side in the dynamic microphone in which the lead wire of the voice coil is wired along the inner surface of the sub dome of the diaphragm facing the ring yoke. Previously, an invention was proposed in which an amplitude restricting means for restricting the lead wire to a position where it does not contact the ring yoke was provided on the magnetism generating circuit side (see Patent Document 1).

  Further, the inventor applied an elastic layer on the inner surface side of the sub dome of the diaphragm adjacent to the voice coil so that the lead wire of the voice coil is not disconnected even when the diaphragm is pressed against the magnetism generation circuit. An invention relating to a dynamic microphone characterized in that the lead wire is elastically held on the sub dome side through a layer has been proposed (see Patent Document 2).

JP 2005-260306 A JP 2006-019791 A

According to the inventions described in Patent Document 1 and Patent Document 2, when a large sound pressure is applied and the diaphragm is greatly displaced, the diaphragm hits a magnetism generating circuit that is a fixed portion and stops the movement of the diaphragm. ing. By adopting such a configuration, an effect of preventing disconnection of the voice coil lead wire can be obtained.
However, there is a difficulty that noise is generated when the diaphragm hits the fixed portion.

  The present invention eliminates the problems of the above-described conventional dynamic microphone unit, that is, a dynamic microphone unit capable of reducing an impact sound generated when the diaphragm is greatly displaced, and a dynamic microphone using the microphone unit. The purpose is to provide.

  The present invention includes a diaphragm that vibrates in response to sound waves, a voice coil that is fixed to the diaphragm and vibrates together with the diaphragm, and a magnetic gap in which the voice coil is disposed to generate a magnetic field in the magnetic gap. A dynamic circuit comprising a magnetic circuit, a rear air chamber formed on the back side of the diaphragm, and a second air chamber formed behind the voice coil and communicating with the rear air chamber. In the microphone unit, a thin plate-like acoustic resistor having elasticity can limit the volume of the second air chamber and the voice coil can be in contact with the second air chamber within the maximum displacement. The most important feature is that the position is applied with tension.

  The volume of the second air chamber behind the voice coil is limited by a thin plate-like acoustic resistor, and resonance between the acoustic mass of the magnetic gap portion and the acoustic capacity of the second air chamber is unlikely to occur, and a good frequency characteristic is obtained. Can get. The thin plate-like acoustic resistor is provided with a tension, and when the voice coil is greatly displaced and comes into contact with the acoustic resistor, the acoustic resistor is bent to cause an impact due to the contact of the voice coil. The force can be relaxed and the generation of noise can be suppressed.

It is a longitudinal cross-sectional view which shows the principal part of the Example of the dynamic microphone unit which concerns on this invention. It is a longitudinal cross-sectional view which shows the state which the voice coil greatly displaced in the said Example, and contacted the acoustic resistor according to FIG. It is a top view which shows the acoustic resistance holding body in the said Example. It is a longitudinal cross-sectional view of the said acoustic resistance holding body. It is a longitudinal cross-sectional view which shows a part of adhering process of the said acoustic resistance holding body and an acoustic resistor. It is a longitudinal cross-sectional view which shows the final form of the acoustic resistance holding body and acoustic resistance body which passed through the said adhering process. It is a longitudinal cross-sectional view which shows an example of the conventional dynamic microphone unit. It is a longitudinal cross-sectional view which expands the principal part and shows the state which the voice coil greatly displaced in the said prior art example. It is an equivalent circuit diagram of a conventional dynamic microphone unit. It is a longitudinal cross-sectional view which expands and shows the principal part of another example of the conventional dynamic microphone unit. It is an equivalent circuit schematic of the conventional dynamic microphone unit shown in FIG.

  Hereinafter, embodiments of the dynamic microphone unit according to the present invention will be described with reference to the drawings, and the dynamic microphone according to the present invention will also be referred to. In addition, the same code | symbol was attached | subjected to the same component as the component of the conventional dynamic microphone unit shown in FIG. 7, FIG. 8, FIG.

  1 and 2, reference numeral 1 denotes a unit case that forms the base of the microphone unit. Similar to the unit case 1 of the conventional example, the unit case 1 has a cylindrical shape with a bottom, and an inner cylinder 11 extending downward from the upper end portion is formed by integral molding on the inner side. A flange 12 extending radially inward is formed at the lower end of 11 over the entire circumference of the inner cylinder 11.

  A magnetic circuit is configured by housing the following magnetic circuit forming member in the inner cylinder 11 of the unit case 1. First, a petri dish-like yoke 2 is fitted in the inner cylinder 11, the yoke 2 is supported by the flange 12 of the inner cylinder 11, and the outer peripheral surface of the peripheral wall of the yoke 2 is the inner peripheral surface of the inner cylinder 11. Is in contact with A disc-shaped magnet 3 having an outer diameter smaller than the inner diameter of the peripheral wall of the yoke 2 is fixed by bonding on the bottom plate of the yoke 2, and a disk-shaped pole piece 4 is fixed on the magnet 3 by bonding. Has been. A ring yoke 21 is fixed to the upper end surface of the peripheral wall of the yoke 2 by adhesion. The pole piece 4 and the ring yoke 21 have substantially the same thickness and are fixed at substantially the same height. The outer peripheral surface of the pole piece 4 and the inner peripheral surface of the ring yoke 21 are opposed to each other with an appropriate interval. The space forms a circular magnetic gap. The magnetic circuit constituent member is housed in the inner cylinder 11, and the upper end surface of the pole piece 4 and the upper end surface of the inner cylinder 11 are at substantially the same height.

  The magnetic flux emitted from the magnet 3 returns to the magnet 3 through a magnetic circuit composed of the yoke 2, the ring yoke 21, the magnetic gap, and the pole piece 4. Therefore, the magnetic flux crosses the magnetic gap. The outer diameter of the magnet 3 is smaller than the outer diameter of the pole piece 4, and an air chamber 9 is formed below the magnetic gap between the outer peripheral surface of the magnet 3 and the inner peripheral surface of the inner cylinder 11. The outer diameter of the magnet 3 is smaller than the outer diameter of the pole piece 4, and an air chamber 9 wider than the magnetic gap is formed on the outer peripheral side of the magnet 3 below the magnetic gap. A plurality of holes 22 are formed in the yoke 2 so as to vertically penetrate a portion corresponding to the bottom, and the holes 22 are a space surrounded by the air chamber 9 and the circular flange 12 of the unit case 1, Is connected to a relatively large air chamber 15 inside the unit case 1. The air chamber 15 is a main air chamber formed on the back side of the diaphragm 5 and is referred to as a rear air chamber. On the other hand, the air chamber 9 at the rear of the magnetic gap is a small air chamber, which is hereinafter referred to as a second air chamber.

  A protruding edge 14 is formed at the upper end of the unit case 1 along the outer periphery of the unit case 1, and the upper end of the unit case 1 is inward of the protruding edge 14 and more than the protruding edge 14. A protrusion 13 is formed at a lower position along a circle concentric with the protrusion 14. The outer peripheral edge of the diaphragm 5 is fixed to the upper surface of the protrusion 13. The diaphragm 5 is made of a synthetic resin or metal thin film, and includes a center dome 51 and a sub dome 52 surrounding the center dome 51 by molding the material. The center dome 51 has a shape obtained by cutting a part of the spherical surface, whereas the sub dome 52 has a partial arc shape in cross section and is formed continuously to the outer peripheral edge of the center dome 51, and the outer peripheral edge of the sub dome 52 is the protrusion 13. It is fixed to the upper surface of the. Since the outer peripheral edge of the sub dome 52 is fixed as described above, the diaphragm 5 vibrates in the front-rear direction (vertical direction in FIG. 7) using the outer peripheral edge of the sub dome 52 as a fulcrum when receiving sound waves. can do.

  The voice coil 6 is fixed to the diaphragm 5 along a circular boundary line between the center dome 51 and the sub dome 52. The voice coil 6 is formed and solidified by winding a thin conducting wire, and one end of the cylindrical shape is fixed to the diaphragm 5. With the outer peripheral edge of the sub dome 52 of the diaphragm 5 fixed as described above, the voice coil 6 is positioned within the magnetic gap, and the voice coil 6 is separated from the ring yoke 21 and the pole piece 4. ing.

  On the front side of the diaphragm 5, an equalizer 8 that also serves as a protective member for the diaphragm 5 is disposed by fixing its outer peripheral edge to the protruding edge 14 of the unit case 1. The ceiling surface of the central portion of the equalizer 8 is formed in a dome shape, and a gap with a constant interval is maintained between the diaphragm 5 and the center dome 51. The equalizer 8 has a plurality of holes 82 for guiding sound waves from the outside to the diaphragm 5.

  When the diaphragm 5 receives a sound wave, the diaphragm 5 vibrates back and forth according to the change in sound pressure, and the voice coil 6 vibrates forward and backward along with the vibration of the diaphragm 5. The voice coil 6 oscillates back and forth, crosses the magnetic flux passing through the magnetic gap, and generates an audio signal corresponding to the change in sound pressure. In this way, electroacoustic conversion is performed, and for example, audio signals are output from both ends of the voice coil 6 routed along the back surface of the subdome 52.

  The major feature of the present embodiment is that a thin plate-like acoustic resistor 50 having an elastic force is connected to the second air chamber 9 to limit the volume of the second air chamber 9 and the voice coil 6 contacts within the maximum displacement. That is, it is arranged with tension applied at a position where it is possible. The second air chamber 9 is formed in a circular shape concentric with the cylindrical voice coil 6 between the outer peripheral surface of the magnet 3 and the inner peripheral surface of the peripheral wall of the yoke 2. A ring-shaped acoustic resistance holder 40 is disposed.

  The structure of the acoustic resistance holder 40 is shown in FIGS. 3 and 4, the ring-shaped acoustic resistance holding body 40 is formed with grooves 42 having a predetermined width along the concentric circles on the upper and lower surfaces thereof. Circular planes 43 and 44 are formed on the circumferential side and the outer circumferential side. The acoustic resistance holding body 40 is formed symmetrically so that there is no problem even if it is turned upside down. In the groove 42, a plurality of holes 41 penetrating the acoustic resistance holding body 40 in the vertical direction (thickness direction) are formed at equal intervals in the circumferential direction. The acoustic resistor 50 is fixed to one surface of the acoustic resistance holder 40 in the vertical direction, in the illustrated example, the upper surface, and the acoustic resistor 50 covers the groove 42 from above. Therefore, the acoustic resistor 50 covers the hole 41 from above.

  5 and 6 show an example of a method of fixing the acoustic resistor 50 to the acoustic resistance holder 40. FIG. FIG. 5 shows a state in which the acoustic resistor 50 is fixed to the upper surface of the acoustic resistance holder 40, but the following steps are performed before reaching the state of FIG. First, the thin plate-like material of the acoustic resistor 50 is bonded to the periphery with an adhesive tape or the like in a state where an appropriate tension is applied on a flat surface plate. The material of the acoustic resistor 50 is a material that can be bent when an external force is applied in a state where an appropriate tension is applied, and that has an appropriate acoustic resistance. One example of such a material is nylon mesh. Next, an adhesive is applied to the inner circumferential surface side plane 43 and the outer circumferential side plane 44 on one side of the acoustic resistance holding body 40, and the material of the acoustic resistance body 50 in a state where tension is applied as described above. Then, the adhesive application surface of the acoustic resistance holding body 40 is pressed, and this state is maintained to cure the adhesive.

  FIG. 5 shows a state where the acoustic resistance holding body 40 is turned upside down after the adhesive is cured and the materials of the acoustic resistance holding body 40 and the acoustic resistance body 50 are fixed. Next, as indicated by arrows in FIG. 5, the material of the acoustic resistor 50 is cut off along the inner periphery and the outer periphery of the acoustic resistance holder 40. Thus, as shown in FIG. 6, the assembly of the acoustic resistance holding body 40 and the acoustic resistance body 50 is completed.

  The acoustic resistance holding body 40 and the acoustic resistance body 50 combined solid are dropped into the second air chamber 9 as shown in FIGS. 1 and 2, and the bottom surface of the acoustic resistance holding body 40 is set to the bottom surface inside the yoke 2. Fixed by contact. In such an assembly mode, the acoustic resistance holding body 40 holds the acoustic resistance body 50 on the side facing the voice coil 6, and the second air chamber 9 is formed by the acoustic resistance holding body 40 and the acoustic resistance body 50. Is limited to a very small volume on the side facing the voice coil 6. The lower end of the voice coil 6 faces the groove 42 of the acoustic resistance holding body 40, and the acoustic resistor 50 that covers the groove 42 from the upper surface side can contact the voice coil 6 within its maximum displacement. Placed in position. In other words, when the voice coil 6 is greatly displaced toward the acoustic resistor 50, the lower end of the voice coil 6 is in contact with the acoustic resistor 50 and the acoustic resistor 50 is bent downward as shown in FIG. It comes to be able to do it.

  The acoustic resistor 50 has an elastic force and is given an appropriate tension and is held above the groove 42 of the acoustic resistance holder 40. Therefore, when the lower end of the voice coil 6 is separated from the acoustic resistor 50, As shown in FIG. 1, it returns to a flat plate shape. Therefore, the acoustic resistor 50 functions as a damper that absorbs the contact energy of the voice coil 6 when the lower end of the voice coil 6 contacts, and absorbs the impact force caused by the contact of the voice coil 6. Eliminates the generation of impact sounds or reduces impact sounds.

  The acoustic resistance holding body 40 does not have a structure in which the acoustic resistance body 50 is directly fixed to the hole 41 that allows the rear air chamber 15 and the second air chamber 9 to communicate with each other. A wide groove 42 is formed over the entire circumference, and the acoustic resistor 50 is fixed so as to cover the groove 42 from above. Therefore, the area in which the acoustic resistor 50 can bend by the contact of the voice coil 6 is expanded more than the area of the groove having a width corresponding to the diameter of the hole 41, so that the voice coil 6 contacts the acoustic resistor 50. The impact noise reduction effect when touching can be enhanced.

  As described for the conventional dynamic microphone, both end lines of the voice coil are fixed along the back surface of the sub dome 52 of the diaphragm 5 so as to output a signal to the outside. Therefore, if the diaphragm 5 is greatly displaced, the end line of the voice coil 6 may hit the corner of a member constituting the magnetic circuit, for example, the ring yoke 21, and the end line may be cut. However, according to the present embodiment, the downward displacement in FIGS. 1 and 2 of the voice coil 6 and the diaphragm 5 to which the voice coil 6 is fixed is regulated by the acoustic resistor 50 as described above. There is also an advantage that the contact between the members constituting the magnetic circuit and the end line of the voice coil 6 can be avoided and the end line can be prevented from being cut.

  According to the above embodiment, the volume of the second air chamber 9 behind the voice coil 6 is limited by the thin plate-like acoustic resistor 50 and the acoustic resistance holder 40 that holds the acoustic resistor 50. Resonance between the acoustic mass and the acoustic capacity of the second air chamber 9 hardly occurs, and good frequency characteristics can be obtained.

  The dynamic microphone unit according to the embodiment described above can be configured by assembling the microphone unit into the microphone case, and further by assembling a microphone connector for outputting the output signal of the microphone unit to the microphone case. Is done.

DESCRIPTION OF SYMBOLS 1 Unit case 2 Yoke 3 Magnet 4 Pole piece 5 Diaphragm 6 Voice coil 8 Equalizer 9 2nd air chamber 15 Rear air chamber 21 Ring yoke 40 Acoustic resistance holding body 41 Hole 42 Groove 50 Acoustic resistance body

Claims (6)

A diaphragm that vibrates in response to a sound wave; a voice coil that is fixed to the diaphragm and vibrates with the diaphragm; a magnetic circuit that includes a magnetic gap in which the voice coil is disposed and generates a magnetic field in the magnetic gap; A dynamic microphone unit comprising: a rear air chamber formed on the back side of the diaphragm; and a second air chamber formed behind the voice coil and communicating with the rear air chamber. And
In the second air chamber, a thin plate-like acoustic resistor having elasticity exerts a tension at a position where the volume of the second air chamber is limited and the voice coil can contact within the maximum displacement. Dynamic microphone unit   The second air chamber is formed in a circular shape concentric with the cylindrical voice coil, and a ring-shaped acoustic resistance holding body is disposed in the circular second air chamber, and the acoustic resistance holding body is connected to the voice coil. The dynamic microphone unit according to claim 1, wherein the acoustic resistor is held on the opposite surface side.   The dynamic microphone unit according to claim 2, wherein the acoustic resistance holding body has a hole connecting the rear air chamber and the second air chamber, and the acoustic resistance body is disposed so as to cover the hole.   4. The dynamic resistor according to claim 3, wherein the hole of the acoustic resistance holding body has a large diameter on the acoustic resistor arrangement surface side, and an area of the acoustic resistance body that can be bent when the voice coil comes into contact is expanded. Microphone unit.   The magnetic circuit has a yoke, a magnet fixed to the yoke, and a pole piece fixed to the magnet. The yoke has a hole for communicating the rear air chamber and the second air chamber. The dynamic microphone unit according to claim 1, wherein the dynamic microphone unit is formed.   A dynamic microphone in which a dynamic microphone unit is incorporated in a microphone case, wherein the dynamic microphone unit is a dynamic microphone unit according to any one of claims 1 to 5.

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